Eli5: what exactly is clay? How is it different from regular dirt or loam?
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Clay is made of very small bits of mineral, which are made when rocks erode. The mineral particles in clay are much smaller than sand or silt, which is why clay can hold so much water: the water molecules stick in between tiny thin layers of clay molecules.
Loam is a soil that’s a mix of lots of different materials, including sand, silt, clay, and organic matter.
Clay is formed from very fine particles of certain hydrated minerals, packed together. Loam is primarily organic material that’s in an advanced state of decomposition, and “dirt” doesn’t really have a strict meaning.
Clay particles are so small you need an electron microscope to see it. Silt particles you would need an optical microscope.
Dirt and soil has sand, silt, and clay size particles, along with organic material.
It’s the size of the particles. Clay particles are so fine that you can’t feel them with your fingers so it feels smooth. Only certain minerals are even capable of being so fine. These “clay minerals” also tend to have a very thin plate-like shape under a microscope. Because the particles have a flat shape, they have a lot of surface area, so they have a tendency to be really cohesive and stick together.
Americans have weird definitions. In ordinary English, dirt has nothing to do with soil or clay. Dirt can be litter, rubbish, stains etc. Ie something that is dirty. We call what Americans refer to as dirt, Earth.
As a young man I worked as a soils mechanic for a construction company.
Clay is flat particles smaller than 200 parts per inch. Silt is round particles, smaller than 200 parts per inch.
Dirt is what gets swept up when you clean the floor. Soil is all of the stuff that you see when you dig into the ground.
Clay is sticky because when they get wet, the flat particles stick to one another. Round particles do not stick together.
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